Method of manufacturing honeycomb structural body

ABSTRACT

A method of manufacturing a honeycomb structure of the present invention is a method of obtaining a honeycomb structure  10  having a predetermined shape by processing a peripheral portion of a crude honeycomb structure  2 , the method being characterized in that the peripheral portion of the crude honeycomb structure  2  is processed by a cutter having linear cut-off device. It is possible to effectively manufacture a honeycomb structure suitably used in a carrier for a catalyst having a catalytic action, for use in internal combustion engine, boiler, chemical reactor, reformer for fuel cell, etc., or as a filter for trapping particulate matter present in an exhaust gas by the method at low cost.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a honeycombstructure. More specifically, the present invention relates to a methodwhich can be low in cost and efficiently manufacture a honeycombstructure suitably used as a carrier for a catalyst having a catalyticaction, for use in internal combustion engine, boiler, chemical reactor,reformer for fuel cell, etc., or as a filter for trapping particulatematter present in an exhaust gas.

BACKGROUND ART

Honeycomb structures are in use as a carrier for a catalyst having acatalytic action, for use in internal combustion engine, boiler,chemical reactor, fuel cell reformer, etc. and a filter for trappingparticulate matter present in an exhaust gas, particularly particulatematter emitted from a diesel engine.

In the honeycomb structure used for such a purpose, the sharptemperature change of exhaust gas and the local heating makesnon-uniform the temperature distribution inside the honeycomb structureand there have been problems such as crack generation in honeycombstructure and the like. When the honeycomb structure is usedparticularly as a filter for trapping a particulate matter in an exhaustgas emitted from a diesel engine (hereinafter the filter is referred asDPF), it is necessary to burn the fine carbon particles deposited on thefilter to remove the particles and regenerate the filter and, in thatcase, high temperatures are inevitably generated locally in the filter;as a result, cracks have tended to be generated by a large thermalstress.

Hence, there have been proposed processes for producing a honeycombstructure by bonding a plurality of individual segments using a bondingagent. In, for example, U.S. Pat. No. 4,335,783 is disclosed a processfor producing a honeycomb structure, which comprises bonding a largenumber of honeycomb parts using a discontinuous bonding agent. Also inJP-B-61-51240 is proposed a thermal shock resistant rotary regenerativeceramic heat exchanger which is formed by extrusion forming a matrixsegment of honeycomb structure made of a ceramic material; firing them;making smooth, by processing, the outer peripheral portion of the firedsegment; coating the part subject to bonding of the resulting segmentwith a ceramic bonding agent which turns, after firing, to havesubstantially the same chemical composition as the matrix segment and adifference in thermal expansion coefficient of 0.1% or less at 800° C.;and firing the coated segments.

Also in the SAE paper 860008 of 1986 is disclosed a ceramic honeycombstructure obtained by bonding cordierite honeycomb segments with acordierite cement. Further in JP-A-8-28246 is disclosed a ceramichoneycomb structure obtained by bonding honeycomb ceramic members withan elastic sealant made of at least a three-dimensionally intertwinedinorganic fiber, an inorganic binder, an organic binder and inorganicparticles.

The honeycomb structure arranged as described above is ordinarilymanufactured by forming honeycomb segments having cells disposedparallel to a central axis of the honeycomb segment, each cell beingsurrounded by porous partition walls functioning as filters, and eachcell functioning as a fluid passage, combining the honeycomb segments toform a crude honeycomb structure, and processing a peripheral portion ofthe crude honeycomb structure in a predetermined shape. Since thehoneycomb structure manufactured as described above is accommodated in ametal can body and the like for use, it must be processed so that it hasan outer peripheral shape corresponding to an inner shape of the metalcan body and the like. That is, it is necessary to manufacture ahoneycomb structure from the crude honeycomb structure described aboveby processing the peripheral portion of the crude honeycomb structure ina shape corresponding to the inner shape of the metal can body and thelike in which the crude honeycomb structure is accommodated.

There has been known a method of processing the peripheral portion ofthe crude honeycomb structure by a grinder, for example, a cam grinder,a cylindrical grinder, and the like as a method of manufacturing thehoneycomb structure. For example, there have been proposed a method ofmanufacturing a honeycomb structure by grinding a porous ceramicmaterial to various sizes and shapes using a grind member having grindstones disposed on the circumferential portion of a disc, and a methodof manufacturing a honeycomb structure having various shapes by moving aposition of a grind member in synchronism with rotation of a porousceramic material under numerical control (NC) using a computer(JP-A-2001-191240).

In the methods described above, however, when a body to be ground(a bodyto be processed) is a crude honeycomb structure 102 formed by combininga plurality of honeycomb segments 101 as shown in FIG. 5 and peripheralportions of the crude honeycomb segments 102 are processed by thegrinder, for example, the cam grinder, the cylindrical grinder, and thelike, there is a problem in that a processing speed is restricted in arange in which the crude honeycomb structure 102 is not broken. This isbecause a rotating direction of a grind stone 103 is in coincidence witha direction in which the honeycomb segments 101 are exfoliated and thecrude honeycomb structure 102 is broken on a bonding surface 104 of thehoneycomb segments 101 constituting the crude honeycomb structure 102.Accordingly, the above methods are disadvantageous in that the crudehoneycomb structure 102 cannot be effectively processed.

Moreover, when the crude honeycomb structure 102 is formed in a shapehaving corners, for example, it is a rectangular parallelepiped as shownin FIG. 5, there is also a problem in that a probability of breakage ofthe crude honeycomb structure 102 is increased by an impact generatedwhen a corner portion of the crude honeycomb structure 102 is ground bythe grind stone 103. Further, since the body to be ground is the porousceramic material and has a high processing resistance due to itshardness, the grind stone 103 is worn at a high speed (has a short lifeas a tool), from which a problem arises in that these methods are notadvantageous in cost.

The present invention has been made in view of the above situation andaims at providing a method which can be low in cost and efficientlymanufacture a honeycomb structure suitably used as a carrier for acatalyst having a catalytic action, for use in internal combustionengine, boiler, chemical reactor, reformer for fuel cell, etc., or as afilter for trapping particulate matter present in an exhaust gas.

DISCLOSURE OF THE INVENTION

As a result of a diligent study for achieving the above object, theinventors have completed the present invention by finding that the aboveobject can be achieved by processing a shape of a peripheral portion ofa crude honeycomb structure by a cutter having linear cut-off device.According to the present invention, following method for manufacturing ahoneycomb structure is provided.

[1] A method for manufacturing a honeycomb structure, the methodcomprising a step of processing a peripheral portion of a crudehoneycomb structure to obtain a honeycomb structure with predeterminedshape, characterized in that the step of processing a peripheral portionof a crude honeycomb structure is made by a cutter having linear cut-offdevice.

With the above arrangement, the honeycomb structure can be effectivelymanufactured at low cost.

[2]. The method for manufacturing a honeycomb structure according to theabove [1], wherein the cutter is a bead saw having a linear cutter asthe linear cutting device comprising a linear body and any of diamondabrasive grain, general grind stone and multi-blade cutter disposed onthe linear body.

[3] The method for manufacturing a honeycomb structure according to theabove [1] or [2], wherein the method comprising steps of forminghoneycomb segments having cells disposed parallel to a central axis ofthe honeycomb segment, each cell being surrounded by porous partitionwalls functioning as filters, and each cell functioning as a fluidpassage; combining the honeycomb segments to form the crude honeycombstructure; processing the crude honeycomb structure by the bead saw toobtain a honeycomb structure with a predetermined shape.

[4] The method for manufacturing a honeycomb structure according to theabove [1] or [2], wherein the method comprising steps of: forminghoneycomb segments having cells disposed parallel to a central axis ofthe honeycomb segment, each cell being surrounded by porous partitionwalls functioning as filters, and each cell functioning as a fluidpassage; combining the honeycomb segments to form the crude honeycombstructure; roughly processing the crude honeycomb structure by the beadsaw to obtain a roughly processed honeycomb structure with apredetermined shape; and finishing the roughly processed honeycombstructure to obtain the honeycomb structure with a predetermined shape.

[5] The method for manufacturing a honeycomb structure according to anyof the above [2] to [4], wherein the step of processing the peripheralportion of the crude honeycomb structure is made by rotating the crudehoneycomb structure about a central axis thereof, causing the linearcutter of the bead saw to travel in a direction of the central axis, andpressing the linear cutter against the crude honeycomb structure from aside face thereof.

[6] The method for manufacturing a honeycomb structure according to theabove [5], wherein the step of processing the peripheral portion of thecrude honeycomb structure is made by one continuous operation after thelinear cutter is pressed against the crude honeycomb structure from theside face thereof.

[7] The method for manufacturing a honeycomb structure according to anyof the above [1] to [6], wherein the peripheral portion of the crudehoneycomb structure is processed such that a sectional shape of thecrude honeycomb structure is formed in a round shape, an oval shape, anelliptical shape, a triangular shape, a polygonal shape, or an irregularshape when it is cut off along a plane perpendicular to the central axisthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) to 1(e) are explanatory views and partly enlarged viewsschematically showing an embodiment of a method of manufacturing ahoneycomb structure of the present invention, wherein FIG. 1( a) shows aprocessing state of a crude honeycomb structure, FIG. 1( b) shows ashape of a honeycomb structure, FIG. 1( c) shows diamond abrasive grainconstituting a linear cutter, FIG. 1( d) shows a general grind stone,and FIG. 1( e) shows amulti-blade cutter constituting the linear cutter,respectively.

FIGS. 2( a) to 2(d) are explanatory views schematically showing anotherembodiment of the method of manufacturing the honeycomb structure of thepresent invention, wherein FIG. 2( a) shows a rough processing state ofa crude honeycomb structure, FIG. 2( b) shows a shape of the crudehoneycomb structure, FIG. 2( c) shows a finishing state of the crudehoneycomb structure, and FIG. 2( d) shows a shape of a honeycombstructure.

FIGS. 3( a) to 3(c) are explanatory views schematically showing a methodof processing of a peripheral portion of the crude honeycomb structureby one continuous operation in the embodiment of the method ofmanufacturing the honeycomb structure of the present invention, whereinFIG. 3( a) shows a simple selvage trimming, FIG. 3( b) shows R selvagetrimming, and FIG. 3( c) shows overall periphery curve processing,respectively.

FIGS. 4( a) and 4(b) are explanatory views and a partly enlarged viewschematically showing a shape of honeycomb segments in the embodiment ofthe method of manufacturing the honeycomb structure of the presentinvention, wherein FIG. 4( a) shows a columnar prism having a squarecross section, and FIG. 4( b) shows a columnar prism having asector-shaped cross section, respectively.

FIG. 5 is an explanatory view showing one example of the conventionalmethod for manufacturing a honeycomb structure.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiment of the method for manufacturing a honeycomb structureaccording to the present invention is specifically described belowreferring to the accompanying drawings. Note that, in the followingdescription, a term “cross section” means “a cross section when it iscut along a plane perpendicular to a central axis of a honeycombstructure or a crude honeycomb structure” unless otherwise specified.

The gist of the method for manufacturing a honeycomb structure of thepresent invention is that processing a peripheral portion of a crudehoneycomb structure to obtain a honeycomb structure with predeterminedshape, wherein the processing a peripheral portion of a crude honeycombstructure is made by a cutter having linear cut-off device.

In this case, a bead saw can be preferably exemplified as the cutter,the bead saw having a linear cutter as a linear cutting device whichincludes a linear body such as a steel wire and the like and any ofdiamond abrasive grain, general grind stone and multi-blade cutter andthe like is disposed on the linear body.

Specifically exemplified is a bead saw having a linear cutter made of anendless steel wire having a diameter of about 4 to 5 mm, a lineartensile strength of about 200 kg and a linear speed of about 30 m/sec.The linear cutter has bead-shaped metal bond materials, which have adiameter of 8 to 10 mm and a length of about 6 mm and are fixed on theendless wire with a pitch of 25 mm, and each of the metal bond materialshas abrasive grain (#40 to #200) buried therein. Otherwise, generalgrind stones or multi-blade cutters having the same shape as above arefixed on the endless wire with the pitch of 25 mm.

FIGS. 1( a) to 1(e) are explanatory view schematically showing oneembodiment of the method for manufacturing a honeycomb structureaccording to the present invention.

As shown in FIG. 1( a), the embodiment is arranged to obtain a honeycombstructure 10 having a shape shown in FIG. 1( b) by forming honeycombsegments 1 having cells disposed parallel to an axial direction of thehoneycomb segment, each cell being surrounded by porous partition wallsfunctioning as filters, and each cell functioning as a fluid passage(forming process is not shown), combining the honeycomb segments 1 toform a crude honeycomb structure 2 (forming process is not shown), andprocessing a peripheral portion of the crude honeycomb structure 2 by abead saw 3 having a linear cutter 4. As shown in a partly enlarged viewof FIG. 1( a), the linear cutter 4 in the embodiment is arranged byfixing the diamond abrasive grain (FIG. 1( c)), the general grind stone(FIG. 1( d)), the multi-blade cutter (FIG. 1( e)), and the like on theendless steel wire and the like described above in a beaded state.

When a body to be processed is the crude honeycomb structure 2, which isformed by combining the honeycomb segments 1 and liable to be broken(when the body is formed in a rectangular parallelepiped shape, it isparticularly liable to be broken) as described above, the honeycombstructure 10 can be effectively manufactured at low cost.

FIGS. 2( a) to 2(d) are explanatory view schematically showing anotherembodiment of the method for manufacturing a honeycomb structureaccording to the present invention.

As shown in FIG. 2( a), the embodiment is arranged to obtain a honeycombstructure 10 shown in FIG. 2( d) by forming honeycomb segments 1 havingcells disposed parallel to a central axis of the honeycomb segment, eachcell being surrounded by porous partition walls functioning as filters,and each cell functioning as a fluid passage (forming process is notshown), combining the honeycomb segments to form a crude honeycombstructure 2 (forming process is not shown), roughly processing aperipheral portion of the crude honeycomb structure 2 by a bead saw 3having a linear cutter 4 to obtain a roughly processed honeycombstructure 2′ having a shape shown in FIG. 2( b) (the shape is slightlylarger than that of a finally obtained honeycomb structure), andfinishing the roughly processed honeycomb structure 2′ by a grind stone103 of a cam grinder 5 as shown in FIG. 2( c). The bead saw 3, and thelike used in the embodiment are the same as those used in the embodimentdescribed above.

As described above, the processing is divided into two steps. First, theperipheral portion of the crude honeycomb structure, which is liable tobe broken, is roughly processed using the bead saw which can conductprocessing without causing breakage of the crude honeycomb structure tothereby form the roughly processed honeycomb structure 2′ having areduced processing margin. Then, the honeycomb structure 2′ is finishedusing the cam grinder. As a result, breakage of the honeycomb structurecan be prevented before it happens by reducing the processing margin aswell as highly accurate processing of the peripheral portion can berealized.

In the embodiment described above, when the peripheral portion of thecrude honeycomb structure 2 is processed using the bead saw 3 as shownin FIGS. 1( a) and 2(a), it is preferable to rotate the crude honeycombstructure 2 about a central axis P as shown in FIGS. 1( a) and 2(a), tocause the linear cutter 4 of the bead saw 3 to travel in a direction ofthe central axis as shown in FIGS. 1( a) and 2(a), and to press thelinear cutter 4 against the crude honeycomb structure 2 from a side facethereof.

With the above arrangement, the linear cutter rotates on its axis whiletraveling in the direction of the central axis of the crude honeycombstructure. Accordingly, the honeycomb structure can be manufactured moreeffectively at low cost utilizing characteristics of the bead saw suchas a processing resistance reducing effect resulting from that an entireperiphery of the cutter contributes to processing, a processingresistance reducing effect resulting from that the processing isconducted intermittently due to the beaded state, a processingresistance reducing effect and a high chip discharging effect resultingfrom that the cutter comes into contact with the body to be processed ina semi-round shape because it is the liner cutter, and an effect that anexcessive force is unlike to be applied to the body to be processedbecause the cutter appropriately sags due to its linear shape.

In this case, it is preferable to process the peripheral portion of thecrude honeycomb structure 2 by one continuous operation after the linearcutter 4 is pressed against the crude honeycomb structure 2 from theside face thereof.

When the peripheral portion of the crude honeycomb structure 2 isprocessed by the one continuous operation (operation without a halt) asdescribed above, any of simple selvage trimming (3(a)), R selvagetrimming (FIG. 3( b)), and overall periphery processing (FIG. 3( c)) maybe used as shown in FIGS. 3( a) to 3(c). Note that FIGS. 3( a) and 3(b)show a case that the crude honeycomb structure 2′ is obtained after theprocessing, and FIG. 3( c) shows a case that the honeycomb structure 10is obtained after the processing (this may be also used in a case thatthe crude honeycomb structure 2′ is obtained after the processing).

With the above arrangement, the honeycomb structure can be moreeffectively manufactured at low cost by utilizing the characteristics ofthe bead saw which can conduct a series of operation without a halt.

Further, it is preferable to process the peripheral portion of the crudehoneycomb structure so that a cross section thereof has a shapecorresponding to an internal shape of a metal can body, and the like inwhich the crude honeycomb structure is accommodated. Otherwise, it ispreferable to process the peripheral portion of the crude honeycombstructure to a predetermined shape, for example, a round shape, an ovalshape, an elliptical shape, a triangular shape, a polygonal shape, anirregular shape, and the like.

With the above arrangement, the characteristics of the bead saw 3described above can be sufficiently utilized.

Further, various shapes of the honeycomb structure may be manufacturedby moving the linear cutter in synchronism with rotation of the crudehoneycomb structure (porous ceramic material) under numerical control(NC) using a computer.

There is no particular restriction as to the method of forming thehoneycomb segment 1, and, in general, any method of manufacturing a bodyhaving a honeycomb structure can be used. For example, the honeycombsegment 1 can be manufactured by the following method.

AS a raw material for the honeycomb segment 1, there is used, at leastone kind of ceramic selected from the group consisting of siliconcarbide, silicon nitride, cordierite, alumina, mullite, zirconia,zirconium phosphate, aluminum titanate, titania and combinationsthereof; a Fe—Cr—Al type metal; a nickel-based metal, a combination ofmetallic Si and Sic; or the like as a major component (the majorcomponent refers to component which constitutes 80% by mass or more ofthe total components and which become a main crystal phase). Thereto areadded a binder such as methyl cellulose, hydroxypropoxyl methylcellulose or the like, a surfactant, water, etc. to obtain kneaded clayhaving plasticity.

The kneaded clay is, for example, extruded to thereby form a honeycombstructure having cells 12 functioning as flow paths disposed parallel toan axial direction as shown in FIG. 4( a), each cell being surrounded byporous partition walls 11. Then, the honeycomb segment 1 as shown inFIG. 4( a) can be manufactured by firing the honeycomb structure afterthe same is dried by, for example, microwaves, hot air, and the like.

Note that when the honeycomb segment is composed of metal Si and SiC, itis preferable that a content of Si defined by Si/(Si+SiC) is 5 to 50% bymass. In this case, it is preferable that a bonding agent contains themetal Si and SiC or any one of them.

There is no restriction as to the cell density (the number of cells perunit sectional area) of the honeycomb segment 1. The cell density ispreferably 0.9 to 310 cells/cm² (6 to 2,000 cells/in.²). Further,although there is no particular restriction as to the sectional shape ofthe cell (cell shape), a polygonal shape such as a triangular shape, asquare shape, a hexagonal shape, and the like, a round shape, anelliptical shape, a corrugated shape, and the like can be exemplified.Among them, the triangular shape, the square shape, and the hexagonalshape are preferable from a view point of production. There is noparticular restriction as to the thickness of the partition wall. Thethickness is in a range of preferably 50 to 2,000 μm.

Further, although there is no particular restriction as to shape of thehoneycomb segment 1, a columnar body having a square sectional shape(quadratic prism) as shown in, for example, FIG. 4( a) can beexemplified. Further, a columnar body having a sector shape as shown inFIG. (4 b) can be also exemplified.

In the embodiment, after the honeycomb segments 1 are manufactured, thecrude honeycomb structure 2 is formed by combining them by bonding themto each other by a bonding agent.

Note that, there is no particular restriction as to the shape of thecrude honeycomb structure 2 having the combined honeycomb segments 1, acolumnar body (rectangular parallelepiped) having a square cross sectionas shown in, for example, FIG. 1( a) can be exemplified. In addition tothe above, the crude honeycomb structure 2 may be a columnar body havinga round cross section, an oval-shaped cross section, an elliptical crosssection, a polygonal cross section, a triangular cross section, and thelike.

A method of, for example, applying a bonding agent to at least one ofconfronting bonding surfaces of two honeycomb segments to be combinedand bonding these bonding surfaces to each other is exemplified as aspecific method of forming the crude honeycomb structure. In this case,bonding is preferably conducted by pressing the to-be-bonded honeycombsegments, because it is easy and good bonding strength can be obtained.In this case, an inorganic or organic spacer, for example, may beinterposed between the honeycomb segments to be combined to obtain ahoneycomb structure with good dimensional accuracy by making uniform athickness of a bonding layer between the honeycomb segments to becombined.

There is no particular restriction as to the type of the bonding agentused in the embodiment, and any known bonding agent suitable for amaterial of the honeycomb segment may be used. For example, a bondingagent, in which inorganic fibers such as ceramic fibers and the like,inorganic powder such as ceramic powder and the like, an inorganic ororganic binder, and the like are blended, is preferably used. Further,the bonding agent may contain a sol-like material such a Si sol, and thelike. A plurality of different bonding agents may be used and, in thiscase, the bonding layer may be formed as a plurality of layers. When thebonding layer is formed as a plurality of layers, the composition of,for example, the bonding layer in contact with honeycomb segment may bemade so as to have a composition close to the composition of thehoneycomb segment and the compositions of other bonding layers maychanged gradually. Further, the bonding agents having at least the twodifferent compositions may be separately applied one by one so that thebonding layer is formed as a plurality of layers. When the bonding layeris formed as a plurality of layers, the composition of, for example, thebonding layer in contact with honeycomb segment may be made so as tohave a composition close to the composition of the honeycomb segment andthe compositions of other bonding layers may changed gradually.Depending upon the kind of the bonding agent used, larger bondingstrength can be obtained by further conducting drying and/or firing.There is no particular restriction as to the thickness of the bondedlayer, it is preferably 0.1 to 3.0 mm.

Further, when the honeycomb structure obtained finally in the embodimentdescribed above is used as filter, in particular, as a DPF, and thelike, it is preferable to plug open end faces of the cells by a sealantso that the end faces are alternately formed in a checkered pattern.Plugging by a sealant can be conducted by masking cells that are not tobe plugged, applying a slurry-state sealant to each open end face ofhoneycomb segment, and drying and firing the resulting honeycombsegment. In this case, the plugging is preferably conducted during theabove-mentioned steps of producing a honeycomb segment, that is, afterforming of honeycomb segment and before firing, because the firing stepmay be once. However, the plugging may be conducted after firing, or atany timing after forming. Further, the crude honeycomb structure, theroughly processed honeycomb body, or the honeycomb body may be pluggedafter they are formed.

The plugging may be conducted after the firing and may be conducted atany timing as long as it is conducted after the forming. The materialfor the sealant used can be appropriately selected from theabove-mentioned group of preferred raw materials for the honeycombsegment, and it is preferred to use the same raw material as forhoneycomb segment.

Further, a catalyst may be carried by the crude honeycomb structure orthe honeycomb structure. Although there is no particular restriction asto the method thereof, a method of carrying the catalyst by, forexample, wash coating, drying, and firing a catalyst slurry can beexemplified. This step also can be conducted at any timing as long as itis conducted after the forming of honeycomb segment.

As mentioned above, when the honeycomb structure obtained by theembodiment is used as a catalyst carrier in an internal combustionengine, a boiler, a chemical reactor, a reformer for fuel cell, etc.,the honeycomb structure is preferred to carry a metal having a catalyticaction. The representative examples of the material having the catalyticaction include Pt, Pd, Rh, and the like. It is preferable to cause thehoneycomb structure to carry at least one kind of these materials.

It is possible to provide the honeycomb structure obtained in theembodiment with a dimensional accuracy of about ±1 mm. This accuracy cansufficiently cope with a case that coating is applied to the peripheralportion at the next step. Further, a honeycomb structure havingexcellent quality without defects such as chipping, cracks, andexfoliation, breakage and the like of bonded faces can be obtained.Further, the liner cutter has a long life and is economical withoutgeneration of eccentric wear.

The method for manufacturing a honeycomb structure according to thepresent invention is described in more detail below by way of Examples.

EXAMPLES 1 TO 5

(Production of a Honeycomb Segment)

A silicon carbide powder and a silicon powder were used as rawmaterials. Thereto were added methyl cellulose, hydroxypropoxyl methylcellulose, a surfactant and water to produce kneaded clay havingplasticity. This kneaded clay was subjected to extrusion, and theresulting extrudate was dried using a microwave and hot air. Then, theformed body was heated (for removing binder) and fired in the atmosphereto obtain a quadrangular prism shaped honeycomb segment such as shown inFIG. 4( a), having a dimension of 58 mm×58 mm×150 mm (height).

There were prepared two honeycomb segments produced above, a paper board(as a spacer) having a dimension of 50 mm×10 mm×0.8 mm (thickness), anda ceramic-made bonding agent composed of 40% by mass of SiC, 20% by massof a silica sol, 1% by mass of an inorganic auxiliary agent, 30% by massof a ceramic fiber and 9% by mass of water. The ceramic-made bondingagent was applied to a side of one honeycomb segment, i.e. the surface,which is to be bonded; the paper board was placed on the upper and lowerareas of the side; and the two honeycomb segments were pressed-bondedand then dried; thereby was obtained a crude honeycomb structure inwhich the two honeycomb segments were combined.

(Processing a Peripheral Portion of the Crude Honeycomb Structure)

Elliptical honeycomb structures each having a long diameter of 185 mm, ashort diameter of 90 mm, and an elliptical cross sectional shape wereformed of a crude honeycomb structure of 230×117×300 mm (height) using,as the bead saw, a Beads One (brand name) of Dainaka Seiki Inc. (diamondwire: diameter; 8 mm, length; 4.6 m, linear speed; 30 m/sec, lineartensile strength; 200 kg, the number of revolution of table; 30 to150/sec, simple selvage trimming, R selvage trimming, and processingwithout a halt can be conducted). Table 1 shows the results ofmeasurement of differences of diameter (degree of cylindricality) atboth the ends and an intermediate position of the thus obtainedhoneycomb structures in a center axis thereof. Note that the sameoperation was conducted five times using the crude honeycomb structureshaving the same size. Resultant crude honeycomb structures are shown asembodiments 1 to 5.

COMPARATIVE EXAMPLES 1 TO 5

Elliptical honeycomb structures each having a long diameter of 185 mm, ashort diameter of 90 mm, and an elliptical sectional shape were formedof a crude honeycomb structure of 230×117×300 mm (height) likewise theembodiments 1 to 5 using only a synchronized cylindrical grinder (brandname; Cam Grinder) of Toyoda machine works, LTD. (diamond grind stone:diameter; 350 mm, thickness; 30 mm, grind stone peripheral velocity; 80m/sec, the number of revolution of work (body to be processed); 10 to 30rpm, peripheral portion can be processed). Table 1 shows the results ofmeasurement of differences of diameter (degree of cylindricality) atboth the ends and an intermediate position of the thus obtainedhoneycomb structures in a center axis thereof. Note that the sameoperation was conducted five times using crude honeycomb structureshaving the same size. Resulting crude honeycomb structures are shown ascomparative examples 1 to 5. A mark “x” in a column of degree ofcylindricality resulting from processing in Table 1 shows thatmeasurement was impossible.

EXAMPLES 6 TO 10

Elliptical honeycomb structures were formed likewise the embodiments 1to 5 except that crude honeycomb structures subjected to R selvagetrimming by a bead saw as rough processing were finished by a camgrinder. Table 1 shows the results of measurement of differences ofdiameter (degree of cylindricality) at both the ends and an intermediateposition of the thus obtained honeycomb structures in a center axisthereof. Note that the two processing steps took the same processingtime (1 minute×twice). The same operation was conducted five times usingcrude honeycomb structures having the same size. The results ofmeasurement are shown as the embodiments 6 to 10.

TABLE 1 Degree of Presence or cylindricality absence of Procesingresulting from breakage of body time processing (mm) to be processedComparative  3 minutes and 0.08 Absent example 1 20 seconds Comparative 3 minutes and X Present example 2 20 seconds Comparative  3 minutes andX Present example 3 20 seconds Comparative  3 minutes and X Presentexample 4 20 seconds Comparative  3 minutes and 0.08 Absent example 5 20seconds Embodiment 1  3 minutes 0.10 Absent Embodiment 2  3 minutes 0.09Absent Embodiment 3  3 minutes 0.10 Absent Embodiment 4  3 minutes 0.10Absent Embodiment 5  3 minutes 0.09 Absent Embodiment 6  2 minutes 0.08Absent Embodiment 7  2 minutes 0.04 Absent Embodiment 8  2 minutes 0.05Absent Embodiment 9  2 minutes 0.08 Absent Embodiment 10  2 minutes 0.08Absent

From Table 1, it can be found that when the processing operation wasconducted using only the cam grinder as in the comparative examples 1 to5, there was a possibility that breakage was generated. When, however,the processing operation was conducted by the bead saw as in theembodiments 1 to 5, it could be conducted without generation ofbreakage. Further, it can be found that when the crude honeycombstructures, which had been subjected to the R selvage trimming by thebead saw as the rough processing, were finished by the cam grinder, thecrude honeycomb structures could be processed with high accuracy withoutbreakage. Note that in the comparative examples to which only the camgrinder was used, there was a case that the bodies to be processed werenot broken as in the comparative examples 1 and 5. However, there was ahigh probability that the bodies to be processed were broken as in thecomparative examples 2 to 4 as well as “degree of cylindricalityresulting from processing” had an accuracy higher than necessary and along processing time of 3 minutes and 20 seconds was consumed by it,which is not satisfactory from a view point of efficiency.

INDUSTRIAL APPLICABILITY

As described above, according to the method for manufacturing ahoneycomb structure of the present invention, there is provided themethod which can be low in cost and efficiently manufacture a honeycombstructure suitably used as a carrier for a catalyst having a catalyticaction, for use in internal combustion engine, boiler, chemical reactor,reformer for fuel cell, etc., or as a filter for trapping particulatematter present in an exhaust gas.

1. A method for manufacturing a honeycomb structure comprising steps of:forming honeycomb segments each having cells disposed parallel to acentral axis of a respective honeycomb segment, each cell beingsurrounded by porous partition walls functioning as filters, and eachcell functioning as a fluid passage; combining the honeycomb segments toform a crude honeycomb structure using a bonding agent; processing aperipheral portion of the crude honeycomb structure to obtain ahoneycomb structure with a predetermined shape; and finishing theprocessed honeycomb structure to obtain the honeycomb structure with thepredetermined shape, wherein the step of processing a peripheral portionof a crude honeycomb structure is made by a cutter having linear cut-offdevice, the cutter is a bead saw.
 2. The method for manufacturing ahoneycomb structure according to claim 1, wherein the cutter is a linearcutter as the linear cutting device comprising a linear body and any ofdiamond abrasive grain, general grind stone and multi-blade cutterdisposed on the linear body.
 3. The method for manufacturing a honeycombstructure according to claim 1, wherein the method comprises step of:processing the crude honeycomb structure by the bead saw to obtain ahoneycomb structure with a predetermined shape.
 4. The method formanufacturing a honeycomb structure according to claim 1, wherein themethod comprising steps of: roughly processing the crude honeycombstructure by the bead saw to obtain a roughly processed honeycombstructure with a predetermined shape.
 5. The method for manufacturing ahoneycomb structure according to claim 2, wherein the step of processingthe peripheral portion of the crude honeycomb structure is made byrotating the crude honeycomb structure about a central axis thereof,causing the linear cutter of the bead saw to travel in a direction ofthe central axis, and pressing the linear cutter against the crudehoneycomb structure from a side face thereof.
 6. The method formanufacturing a honeycomb structure according to claim 5, wherein thestep of processing the peripheral portion of the crude honeycombstructure is made by one continuous operation after the linear cutter ispressed against the crude honeycomb structure from the side facethereof.
 7. The method for manufacturing a honeycomb structure accordingto claim 2, wherein the peripheral portion of the crude honeycombstructure is processed such that a sectional shape of the crudehoneycomb structure is formed in a round shape, an oval shape, anelliptical shape, a triangular shape, a polygonal shape, or an irregularshape when it is cut off along a plane perpendicular to the central axisthereof.
 8. The method for manufacturing a honeycomb structure accordingto claim 2, wherein the method comprising step of: processing the crudehoneycomb structure by the bead saw to obtain a honeycomb structure witha predetermined shape.
 9. The method for manufacturing a honeycombstructure according to claim 2, wherein the method comprising steps of:roughly processing the crude honeycomb structure by the bead saw toobtain a roughly processed honeycomb structure with a predeterminedshape.
 10. The method for manufacturing a honeycomb structure accordingto claim 3, wherein the step of processing the peripheral portion of thecrude honeycomb structure is made by rotating the crude honeycombstructure about a central axis thereof, causing the linear cutter of thebead saw to travel in a direction of the central axis, and pressing thelinear cutter against the crude honeycomb structure from a side facethereof.
 11. The method for manufacturing a honeycomb structureaccording to claim 4, wherein the step of processing the peripheralportion of the crude honeycomb structure is made by rotating the crudehoneycomb structure about a central axis thereof, causing the linearcutter of the bead saw to travel in a direction of the central axis, andpressing the linear cutter against the crude honeycomb structure from aside face thereof.
 12. The method for manufacturing a honeycombstructure according to claim 2, wherein the peripheral portion of thecrude honeycomb structure is processed such that a sectional shape ofthe crude honeycomb structure is formed in a round shape, an oval shape,an elliptical shape, a triangular shape, a polygonal shape, or anirregular shape when it is cut off along a plane perpendicular to thecentral axis thereof.
 13. The method for manufacturing a honeycombstructure according to claim 3, wherein the peripheral portion of thecrude honeycomb structure is processed such that a sectional shape ofthe crude honeycomb structure is formed in a round shape, an oval shape,an elliptical shape, a triangular shape, a polygonal shape, or anirregular shape when it is cut off along a plane perpendicular to thecentral axis thereof.
 14. The method for manufacturing a honeycombstructure according to claim 4, wherein the peripheral portion of thecrude honeycomb structure is processed such that a sectional shape ofthe crude honeycomb structure is formed in a round shape, an oval shape,an elliptical shape, a triangular shape, a polygonal shape, or anirregular shape when it is cut off along a plane perpendicular to thecentral axis thereof.
 15. The method for manufacturing a honeycombstructure according to claim 5, wherein the peripheral portion of thecrude honeycomb structure is processed such that a sectional shape ofthe crude honeycomb structure is formed in a round shape, an oval shape,an elliptical shape, a triangular shape, a polygonal shape, or anirregular shape when it is cut off along a plane perpendicular to thecentral axis thereof.
 16. The method for manufacturing a honeycombstructure according to claim 6, wherein the peripheral portion of thecrude honeycomb structure is processed such that a sectional shape ofthe crude honeycomb structure is formed in a round shape, an oval shape,an elliptical shape, a triangular shape, a polygonal shape, or anirregular shape when it is cut off along a plane perpendicular to thecentral axis thereof.
 17. The method for manufacturing a honeycombstructure according to claim 1, wherein the cut-off device rotates aboutan axis of the cut-off device in addition to moving in a lineardirection.
 18. The method for manufacturing a honeycomb structureaccording to claim 1, wherein the predetermined shape is a non-roundshape.
 19. The method of manufacturing a honeycomb structure accordingto claim 1, wherein the bead saw comprises an endless wire and aplurality of bead-shaped members made of metal bond material, thebeed-shaped members being fixed on the endless wire at a predeterminedpitch.
 20. The method for manufacturing a honeycomb structure accordingto claim 19, wherein: the endless wire is made of steel and has adiameter between about 4 and 5 mm; the bead-shaped members each has adiameter between about 8 and 10 mm and a length of about 6 mm; and thepitch is about 25 mm.
 21. The method for manufacturing a honeycombstructure according to claim 1, wherein the processing is performed inone continuous operation and includes any of selvage trimming and Rselvage trimming.
 22. The method for manufacturing a honeycomb structureaccording to claim 1, wherein the finishing includes grinding theprocessed honeycomb structure.